Revisiting Pt/TiO2 photocatalysts for thermally assisted photocatalytic reduction of CO2

Abstract

Artificial photosynthesis by a semiconductor–oxide-based photocatalysis is presently challenging due to low CO₂ conversion rates and poor product selectivity. To promote CO₂ reduction, Pt/TiO₂ has been deemed as a classic photocatalyst. In this study, we restudy Pt/TiO₂ for the thermally assisted photocatalytic reduction of CO₂ and reveal a different story between photocatalysis and photothermal catalysis. For example, when using disordered Pt/TiO_2−x, the CO₂ conversion via photocatalysis at 298 K is not impressive. However, when the system temperature is increased to 393 K, the CO₂ conversion rate is significantly enhanced by a factor of 155 as compared to that obtainable from pristine TiO₂; further, surprisingly high selectivity of CH₄ (87.5%) could be achieved. Thermally coupled photocatalysis yields the enhanced evolution of H₂ side products over Pt (4.06 nm)/TiO₂ and promoted H₂ splitting over Pt (2.33 nm)/TiO₂, which is seldom observed in conventional Pt/TiO₂ photocatalysis. The synergy of improved charge separation at the Pt/TiO_2−x interface induced by surface disordering and accelerated H₂ consumption near smaller Pt nanoparticles by thermal assistance are believed to be critically important for the simultaneous enhancement of CO₂ conversion rates and CH₄ product selectivity. This study inspires revisiting not only Pt/TiO₂ but also reactivating other semiconductor–oxide-based photocatalysts for use in thermally assisted photocatalysis.